Low profile electrical plugs are typically manufactured using an injection molding method. U.S. Pat. No. 5,182,032 to Dickie discloses an injection molding apparatus in which non-rigid or flexible components intended to be encapsulated within the interior of an injection molded product is provided.
Although injection molding is an effective method of manufacturing of low profile electrical plugs, it has been determined that ultrasonic welding the desired portions of the plug is a more accurate and less expensive procedure. In addition, injection molding requires that the same material be used to encapsulate the electrical components within the plug, making it difficult to produce hollow cavities and incorporate dissimilar materials to act as transparent or translucent windows. As such, if the plug is to incorporate an electrically illuminated lamp, as in the present invention, injection molding of the plug becomes problematic
Ultrasonic assembly is well-known, and is suitable for most thermoplastic materials. In practice, high-frequency (ultrasonic) energy is transmitted by the ultrasonic welding apparatus to compatible plastic parts. At the intersection of the two parts, a combination of applied force and surface and/or intermolecular friction increases the temperature until the melting point of the thermoplastic is reached. Upon removal of the ultrasonic energy, a bond is produced between the plastic parts, effectively affixing them together in the desired fashion.
Typical systems used for ultrasonic welding contain a high-frequency power supply (20-40 kHz). Energy from the power supply is directed into a horn dimensioned to be resident at the applied frequency. Upon contact with the workpiece, the horn transmits the energy into it. The two parts to be welded are aligned in the proper fashion by a support constructed of aluminum or steel.
Accordingly, it is therefore a general object of the present invention to provide a method of manufacturing a low profile, illuminated electrical plug using an ultrasonic welding process that is less expensive and more accurate than conventional injection molding methods.